Vapor electric device



Feb. 1, 1938. .J. SLEPIAN ET AL. 2,106,857

VAPOR ELECTRIC DEVICE Filed July26, 1955 WITNESSES: j INVENTORS osephSlap/an and lean/610044099 7 4 mm mm ATTORN EY Patented at. 1, 1938UNITED. sr i'rss PATENT OFFICE Forest Hills, Pa., assignors toWestinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., acorporation of Pennsylvania Application July 26, 1935, Serial No. 33,292

6 Claims.

Our invention relates to a vapor electric device and particularly tomeans for maintaining the valve action of the electrodes of such adevice during periods of application of inverse potential to one of theelectrodes.

In the application of arc-type valve devices, it is desirable to haveoneor more of the electrodes, withstand negative potential or inversepotential for definite periods without the formation of an inverse arcto the electrode. This is particularly desirable in such devices asIgnitron inverters, where the cathode which is usually composed ofmercury or vaporizable compounds is required to withstand a highnegative potential during the major portion of its inactive period.Also, in

mercury are devices in which all of the electrodes are composed whollyor in part of mercury, it is desirable that one or all of the electrodesshould be capable of withstanding negative potential without breakingdown.

It has been observed that when substantially pure mercury is used forforming the electrodes and the devices are properly treated out, theelectrodes will successfully withstand periodic or sustainedapplications of inverse potential without the formation of an inversearc so that the device is said to have a high negative reluctance.However, in operation, the electrodes soon become polluted or dirtyafter this has occurred, the electrodes have a very much lower negativereluctance.

We have discoveredthat this lowered negative reluctance is apparentlycaused by accumulations of dirt or other impurities on the surface ofthe electrodes. It has been observed that when a mercury electrodecovered with patches of compounds such as nitrogen compounds is exposedto an inverse potential, the space discharge to the polluted electrodeconcentrates at the patches of impurities, which concentration tends toproduce a cathode spot on the involved electrode and frequently resultsin an inverse are or backfire originating at the dirty spots.

It is accordingly an object of our invention to provide a vapor electricdevice which is maintained substantially free of arc backs. We havefound that this can be accomplishedby introducing into the device aquantity of reducing gas which will combine with the impurities such asnitrogen and other material normally found in or evolved in suchconverters. This gas should be of a kind such as carbon monoxide orhydrogen which forms stable compounds with the impurities.

In certain types of vapor electric devices such as make-alive valves, itis frequently desirable to place the anode in proximity to and directlyexposed to the cathode and then to strongly cool the anode so that theanode is in effect a condenser for the vapor given off by the cathode. 5

Such devices have heretofore had an undesirable backfire rate as theanode surface is wholly or partially covered with condensed mercury andany impurities in the mercury tend to remain on the anode surfaceproviding a patch having a 10 converter. Preferably, a quantity ofreducing gas 15 such as carbon monoxide is provided slightly in excessof the quantity of residual foreign gases usually found in such adevice.

As the carbon monoxide combines with impurities, such as nitrogen,- inthe device, it is desirable ,to replace the combined material with freshgas. While, of course, this could be accomplished by means of'suitablecontainers con nected to the device, we prefer to evolve the replacementgas inside the converter. This can be accomplished by providing in theconverter a quantity of material which, during normal operation of thedevice, evolves carbon monoxide.

We have found that the composition resistance material known as Zircon,when heated, will evolve a satisfactory amount of carbon monoxide tomaintain the monoxide pressure in the device.

Other objects and advantages of our invention will be apparent from thefollowing detailed description taken in conjunction with the accom- 35ing strongly cooled so that it acts as a condenser for the vapor. Thevalve container is completed by a suitable ring 3, preferably ofinsulating material or any suitable material insulated from the anodeand cathode and in vacuum tight relation thereto. such as a make-aliveelectrode 4 having a stem 5 of conducting material and a tip 6 ofresistance material is placed in contact with the cathode l and by thepassage of current therethrough operates to create a cathode spot andcontrol the 55 A suitable excitation electrode 50 only a slight flow ofgas into the container.

conducting are in the device. During pure and clean and the negativereluctance of theoperaflonofthisdevicathecoolcdcathodcl-.thedeviceisnotim thepressureofthenormalresidualgasesfound- This carbonmonoxide combines with impurities already in or evolved in the device toproduce stable compounds which are not detrimental to the operation ofthe device. During the operation, the carbon monoxide or other reducinggas is consumed-so that the pressureisdiminished. Ifthevalvedeviceissubstantially leak-proof and the device has been thoroughlytreated out, the diminished gas pressure my be permitted. For mostdevices, it is desirable. to maintain the quantity of reducing materialin the converter. In order to maintain the pressure, fresh gas must beadded from a suitable source.

2 We have found that the make-alive electrode 4 may be composed whollyor in part of such gas evolving material. The gas may be supplied from asuitable container such as a pressure flask connected to the containerby a valve which permits The gas may also be evolved in the containerand thus eliminate the complication of flask and valves. This maybeaccomplished by placing a quantity of material in the container whichwill evolve the necessary gas preferably by suitable excitation such asthe application of heat or the e of electric current therethrough. Wehave found that the resistance compound, composed essentially ofzirconium silicate with a clay binder and a small percentage of lampblack to control the conductivity, sold under the trade name of Zirconwill, when heated, by the passage of make-alive current therethroughevolve a sufllcient quantity of gas to replace that consumed in theoperation of the device and thus maintain the gas pressure substantiallyconstant. This resistor material may be utilized as the make-alive tip 6or inserted between the stem 5 and a tip 8 of suitable resistancematerial such as carborundum or boron-carbon compositions such as boroncarbide.

Since the carbon monoxide or other reducing gas consumes the deleteriouscompounds normally found in the device, the mercury surfaces both of thecathode and of the condensed mercury on the anode will be keptsubstantially pure so that the negative reluctance is not reduced andthere will be little tendency for the formataminated with foreignmaterial and of very low negative resistance with consequent frequentbreakdown and undesired arcs formed in the device. We have found that byadding a quantity of reducing gas, such as carbon monoxide, the

7 mercury surfaces are maintained su stantia y In the operation of thisdevice, itis desirable to renew or maintain the quantity of reducing gasin the container. This may be easily accomg plished by providing aquantity of suitable material inside the container and providing meansfor heating the material whenever it is desired to evolve more of thereducing gas. While any suitable means may be provided for heating thegas 10 evolving material, we prefer to form the gas evolving materialinto a suitable resistance body It and ,to heat the same by passing anelectric current from any suitable source such as a bate r While, forpurposes of illustration, we haveshown and described particularembodiments of the invention, it will be apparent to those skilled inthe art that many changes and modifications can be made thereon withoutdeparting from the 20 true spirit of our invention'or the scope of theappended claims. 1

We claim as our invention:

1. An electric valve comprising a m cathode, an anode closely spacedfrom and .di- 20 rectly exposed to said cathode, said anode serving as acondenser for the vapor emitted from said cathode, said anode-condenserduring normal operation of said valve being subject to periods ofinverse potential and means for maintaining 80 the negative reluctanceduring said periods, said means including a quantity of carbon monoxideat a pressure of several microns in said valve. a make-alive electrodein said valve, at least a portion of said make-alive electrodeconsisting of a material which will evolve carbon monoxide on thepassage of current therethrough.

2. An electric valve comprising a substantially evacuated container, avaporizable cathode in said container, a strongly cooled anode closely40 spaced with respect to said cathode so. that said cooled anodecondenses the vapor given of! by the cathode whereby said anode isnormally at least partially covered with cathode material and a quantityof carbon monoxide in said container, 45 said carbon monoxide being inquantity greater than the residual foreign gas in said container, andmeans for replenishing the carbon monoxide in said container.

3. An electric valve comprising a substantially evacuated container, apair of main electrodes in said container each of said electrodes,during normal operation, being composed at least in part of mercury, anauxiliary electrode associated with one of said main electrodes, saidauxiliary elec- 55 trade being adapted for initiating a cathode spot onsaid main electrode, and a filling of carbon monoxide in said container,said carbon monoxide having a pressure five to ten times greater thanthat of the residual foreign gases in the go container, and meansactuated by current flow in said auxiliary electrode for replenishingthe carbon monoxide.

4. An electric valve comprising a substantially evacuated container, apair of main electrodes in 55 said container each of said electrodes,during normal operation, being composed at least in part of vaporizablecatnode material, an auxiliary electrode associated with one of saidmain electrodes, said auxiliary electrode being adapted for initiat- 70ing a cathode spot on said main electrode, and a filling of carbonmonoxide in said container. said carbon monoxide having a pressure fiveto ten times greater than that of the residual foreign gases in thecontainer, and means actuated by current flow in said auxiliaryelectrode for replenishing the supply of carbon monoxide in saidcontainer. 7

5. An electric valve comprising a substantially evacuated envelope, atleast two main electrodes therein both of which normally have at least aportion of their surface covered with mercury, at least one of saidelectrodes being required to withstand inverse potential withoutbreaking down, a quantity of carbon monoxide in said envelope, and meansincluding a carbon monoxide evolving material for maintaining thequantity of carbon monoxide.

6. A vapor electric valve comprising a pair of main electrodes, at leastthe surface of said electrodes being covered with mercury, a make-aliveelectrode for initiating current fiow in said valve,

means for maintaining the negative reluctance of said valve comprising aquantity of carbon monoxide in the space between said electrodes, andmeans associated with said make-alive electrode for maintaining thequantity of carbon monoxide.

JOSEPH SLEPIAN. LEON R. LUDVVIG.

